Breast cancer affects a major segment of the female population over the age of 40. To reduce the mortality from this disease, it is vital to diagnose it as early as possible. If breast cancer is detected early enough, chances of a cure are markedly higher. Accordingly, breast cancer screening projects designed for early detection of breast cancer have proven to dramatically reduce the mortality from the disease. Because breast cancer is such a major public health problem, many health authorities worldwide recommend that women undergo routine breast examination.
Today, the standard methods for detecting breast cancer are 1) self examination; 2) clinical examination; and 3) radiography of the breast, known as mammography. Routine mammography screening can reduce mortality from breast cancer. The American Cancer Society recommends that a baseline mammogram be taken between the ages of 35 and 39, every one to two years between the ages of 40-49 and annually on women aged 50 years and older.
The main objective of screening mammography is to detect breast cancer early, before it is palpable. The standard mammographic procedure is to take two views of each breast with specially designed mammography equipment. The breast is optimally positioned so that as much tissue as possible can be examined. The radiologist visually examines the mammographic images on a light box. Using a magnifying glass, the radiologist examines each image in detail. If the radiologist detects any suspicious findings on mammographic examination, he or she may suggest a biopsy of the suspicious area. Suspicious findings include any abnormalities in the breast tissue. Abnormalities may be either malignant or benign, and many times the radiologist cannot diagnose precisely the type of abnormality from the image. Additionally, it has been established that 10-30% of women who indeed have breast cancer have negative mammograms.
There are four possible outcomes in screening mammography:
1) True positive: Earlier detection, treatment and better prognosis; PA0 2) True negative: Reassurance of no cancer; PA0 3) False positive: Anxiety and time, cost and risks of more tests; and PA0 4) False negative: Delay in diagnosis and treatment. Worse prognosis.
The technical interpretive expertise of the radiologist is a crucial factor in effective breast cancer detection. A standard non-invasive procedure does not exist to diagnose a patient after a finding has been detected by mammography. When there is a suspicious finding, a biopsy is frequently performed. Because the information on the mammogram many times is ambiguous, in order not to miss the diagnosis of cancers, many biopsies are performed for mammographic abnormalities. Approximately 70% of these biopsies turn out to be benign.
Although there have been many improvements in the mammographic equipment over the last 10 years, technical impediments limit the ability of mammography to display the finest or most subtle details in good contrast. In order to achieve specific diagnoses, the radiologist needs to visualize the infrastructure of the mammographic abnormality.
Currently, cancers imbedded in dense breast tissue are found at later stages than those in breasts with high fat percentage of tissue. These cancers in dense breasts, in particular, need an earlier detection method. Although radiologists specializing in mammography have stated that the constraints of conventional mammography can be overcome by digital image processing, an effective digital diagnostic assistance approach has not yet been available.